1. Field of the Invention
The present invention generally relates to interactive image viewing systems, and more specifically to an image viewing system that broadcasts images, augmented with point-of-interest overlays, over a video bus to multiple local users, which simultaneously extract and display different viewpoints of the images in real time with a uniform angular resolution over all viewer orientations.
2. Description of the Related Art
Known interactive image viewing systems allow a single person to view his surroundings through an external camera where those surroundings are either remotely located or otherwise occluded from view. Typically, the person wears a head mounted display (HMD), which is fitted with a tracking device that tracks the movement of the person's head. The HMD displays the portion of the surroundings that corresponds to the person's current viewpoint, i.e. head position.
Fakespace, Inc. produces a teleoperated motion platform, the MOLLY.TM., which is used for telepresence and remote sensing applications. The user wears a HMD to view his surroundings. An external stereo camera setup is slaved to the user's head movement so that the cameras track his head movement and provide the desired view of the surroundings. The user's field-of-view (FOV) is approximately 350.degree., of which the user can view approximately 80.degree. at any one time using Fakespaces's BOOM head-coupled display. By slaving camera movement to head position, the displayed image is optimal in the sense that it is the same as if the user turned and looked in that direction absent any occlusion. As a result, the angular resolution of the displayed image is the same at any viewing orientation. However, because the external camera is slaved to a particular user's head movement, the system is limited to a single user and does not support multiple views simultaneously
In a more general application of the slaved camera if the camera is remotely located from the user, the time delay between head movement and image presentation is distracting. If the time delay exceeds a certain limit the user will be unable to experience realistic sensations of interacting with the imagery, may lose his sense of orientation, and in the worst case, may even experience motion sickness.
To address the time delay problem, Hirose et al developed a "Virtual Dome" system, which is described in "Transmission of Realistic Sensation: Development of a Virtual Dome" IEEE VRAIS pp. 125-131, January 1993. In the Virtual Dome system, a single external camera pans and tilts to capture a complete image of the surrounding area. The component images are transmitted to a graphics workstation that texture maps them onto a set of polygons that construct a spherical dome, which in turn provides a virtual screen. By using the HMD, the user can experience remote synthetic sensations by looking around inside the virtual screen.
Due to the intense complexity of the texture mapping process, the user requires a graphics workstation to construct the virtual screen, the image resolution is quite low, and the response to head movements is not real-time. To improve response time, once the system has generated an entire image the camera is then slaved to the user's head movement. As a result, when the user changes his head orientation, he will initially see previously obtained images for only a few seconds until the texture mapping process can recover. However, by slaving the camera motion to the user the system is limited to a single user.
A related technology is embodied in "Virtual Reality" systems, as described in "Virtual Reality: Scientific and Technological Challenges" National Research Council, Nathaniel Durlach and Anne Mavor, Eds, National Academy Press, 1995, p. 17-23. In Virtual Reality systems a single user interacts with computer generated imagery. The user's actions change not only his view of the imagery but the imagery itself.